BMW $50,000 Four-Cylinder Roadster Crashes Party

Like cops shutting down a raucous
frat night, federal gas-mileage restrictions are busting up the
binge that’s led sports-car companies to make ever more powerful
autos. The party’s over.

With corporate average fuel economy set at 34.1 miles per
gallon by 2016, 500-hp supercars that chug petrol by the kegful
are going to need a dose of aspirin.

Which brings us to the latest BMW Z4 convertible, with a
new, less-powerful engine. Available this autumn, it’s the first
four-cylinder from the company in a dozen years.

To sports-car enthusiasts, that probably sounds like a big
uh-oh.

The change is making my head throb all right, but in a good
way. I’m slinging the roadster along a mountain road shaped like
an EKG readout. While the abstrusely named Z4 sDrive28i is less
powerful than its six-cylinder predecessor, I’m not missing
those two extra chambers one bit.

The two-seat, hardtop roadster starts at $49,525 and is
better-balanced than the naturally aspirated sDrive30i it
replaces.

Horsepower may have dropped to 240, from 255, but torque
has increased to 260 pound feet from 220. Which means it has
more grunt from a standstill and ample power in lower gears,
perfect for scrambling through mountain passes -- the kind of
thing buyers are actually looking for in a roadster.

BMWs are typically electronically limited to 130 mph or 150
mph. When was the last time you saw a U.S. road where those
speeds were legal? I can’t really see any downsides to the new
engine. With less weight in the nose, the Z4 feels like it just
kicked a bad habit and has a new spring in its step.

Gas

BMW says gas mileage is improved about 20 percent in the
model with the new eight-speed automatic. EPA numbers aren’t
released yet, but I saw approximately 21 mpg in the city and 33
on the highway in my test car with a six-speed manual, versus
the previous model’s 18 and 28. (A turbocharged 3.0-liter six-
cylinder is also available on the sDrive35i and even more
powerful sDrive35is. They start at $56,025 and $65,075
respectively, with 300 hp and 335 hp.)

I realize that driving enthusiasts are supposed to worship
at the altar of 12-cylinder engines. And no question, the
monumental wall of sound emanating from the hood of an Aston
Martin DBS or Ferrari 599 gives me the happy shivers.

Yet the idea that performance comes only from a high-
displacement V-12 or W-12 is kind of like saying that Big Ben is
inherently a better time keeper than your Casio digital watch.
The former is impressive, but the latter is a heck of a lot more
efficient.

Turbo Charged

BMW is justifiably proud of its new 2.0-liter engine, which
has direct injection, a twin-scroll turbocharger and variable
valve management.

“I think we made a lot of people nervous when we announced
that BMW was bringing four-cylinder engines back to the U.S.
market,” said Paul Ferraiolo, head of product planning and
strategy in the U.S. “But the new engine has the power of a
six-cylinder with the efficiency of a four.”

The last Z4 I had on the racetrack swiveled neatly on
rolling turns, yet felt a tad dull. It just wasn’t as hungry as
I’d like in a small two-seater. Like the latest Mercedes-Benz
SLK convertible which I recently reviewed, the Z4 makes no claim
to a practical nature, so it better be fun.

Nice Noise

The new engine achieves peak torque at a low 1,250 rpm, so
it pulls hard very quickly. Every time I slap down on the gas
pedal the car suddenly comes alive, vibrating and making a nice
noise, visceral and vital.

Of course, prospective buyers and onlookers won’t actually
see the motor. Rather they’ll notice things like the nuclear
yellow the car is available in, and the fact it looks athletic
and fun with the top both up and down.

The 1990s Z3 from which the Z4 evolved was a fragile-
looking, dorky thing. This Z4 is anything but.

BMW’s roadster is a niche car, however, hardly one of the
company’s biggest sellers. To prove that the Munich-based
automaker is serious about its new four-cylinder, the engine
will also make its way into the 5 Series sedan. Yep, the 2012
528i will be available this autumn as a four-banger. I never
thought I’d see the day.

Who says efficiency can’t be fun?

The 2012 BMW Z4 sDrive28i at a Glance

Engine: 2.0-liter, turbocharged four-cylinder with 240

horsepower and 260 pound-feet of torque.

Transmission: Six-speed manual or eight-speed automatic.

Speed: 0 to 60 mph in 5.5 seconds.

Gas mileage per gallon: 21 city; 33 highway (estimated).

Price as tested: $58,225 (estimated).

Best feature: Efficiency without sacrifice.

Worst feature: $50,000 is a spendy starting price.

Target buyer: The sports driver who isn’t afraid to go

smaller.

(Jason H. Harper writes about autos for Muse, the arts and
leisure section of Bloomberg News. The opinions expressed are
his own.)

To contact the writer of this column:
Jason H. Harper at Jason@JasonHharper.com
or follow on Twitter @JasonHarperSpin.